QT DEFINES 是否与 C++ 中的 #define 做同样的事情？
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Is the QT DEFINES doing the same thing as #define in C++?
提问by Terence Chow
What does the DEFINES += includthisvariabledo in QT for a .profile?
什么是DEFINES += includthisvariable在QT一个做.pro文件？
If it works like the #definein C++, where is includethisvariabledefined so that the preprocessor can replace includethisvariablewith the value I set?
如果它像#define在 C++ 中一样工作，那么在哪里includethisvariable定义以便预处理器可以用includethisvariable我设置的值替换？
I understand what #definedoes in c++ because you set the value beside what you define. However here it seems like you just list a name...The QT docs didn't help explain this for me.
我了解#defineC++ 中的作用，因为您将值设置在您定义的值旁边。但是在这里，您似乎只是列出了一个名称……QT 文档并没有帮助我解释这一点。
回答by Michael Burr
The items in the Qt Project file's DEFINESvariable end up on the compiler's command line with the -Doption (or whatever is appropriate for the compiler being used). To give your macro definition a value instead of merely defining it, use the following:
Qt 项目文件DEFINES变量中的项目以-D选项（或任何适合正在使用的编译器的方式）在编译器的命令行中结束。要为您的宏定义提供一个值而不是仅仅定义它，请使用以下命令：
DEFINES += FOOBAR=foobar_value
That will show up on the compiler's command line as -DFOOBAR=foobar_value
这将在编译器的命令行上显示为 -DFOOBAR=foobar_value
If you need spaces you need to quote the value - and escape the quotes that'll be passed on the compiler command line:
如果需要空格，则需要引用该值 - 并转义将在编译器命令行上传递的引号：
DEFINES += FOOBAR="\"foobar value\""
This one shows up as: -DFOOBAR="foobar value"
这个显示为： -DFOOBAR="foobar value"
回答by suspectus
Yes it works in the same way. DEFINES += includethisvariableincludes the pre-processor symbol includethisvariablein the sources being compiled.
是的，它以相同的方式工作。在正在编译的源DEFINES += includethisvariable代码includethisvariable中包含预处理器符号。
This means any #ifdef statements like
这意味着任何 #ifdef 语句，如
#ifdef includethisvariable
...
...
#endif
are included in the source being compiled.
包含在正在编译的源代码中。
Macros with values can also be defined
也可以定义带有值的宏
`DEFINES += "MAXBUFFERSIZE=4096"
回答by Bar?? Akkurt
From the documentation:
从文档：
The defines are specified in the .config file. The .config file is a regular C++ file, prepended to all your source files when they are parsed. Only use the .config file to add lines as in the example below:
定义在 .config 文件中指定。.config 文件是一个常规的 C++ 文件，在解析时添加到所有源文件中。仅使用 .config 文件添加行，如下例所示：
#define NAME value
回答by Adam Zahran
If you'd like to define a macro of a string literal in your qmake file, equivalent to #define VAR "Some string"
如果你想在你的 qmake 文件中定义一个字符串文字的宏，相当于 #define VAR "Some string"
It's gonna look like this:
它看起来像这样：
DEFINES += CODE_WORKING_DIR=\\"$$PWD\\"
So that it would produce that as an argument to g++ (or whatever you're using to compile):
这样它就会产生它作为 g++ 的参数（或者你用来编译的任何东西）：
g++ -c -DCODE_WORKING_DIR=\"/path/to/my/code\"
It is ugly. If someone knows a better way, please let me know.
它很丑。如果有人知道更好的方法，请告诉我。
